Binary decoding system



Nov. 3, 1953 A. ABATE BINARY DECODING SYSTEM Filed March 29, 1950 1m mmsV wm Patentes Nov. s, 1955s BINARY DECODING SYSTEM Anthony Abate,Waltham, Mass.,

assignor to Raytheon Manufacturing Company, Newton, Mass., a corporationof Delaware Application March 29, 1950, Serial No. 152,680

(Cl. Z50-27) Claims.

This invention relates to decoding of binary digital code information.

in many instances, it is desirable to convert binary coded intelligenceto voltage signals whose amplitude determines the convertedintelligence. For instance, where original information has been in thenature of varying amplitude voltage signals and has been converted tobinary code numbers to take advantage of ease in transmission andstorage in this form, it often becomes desirable to reconvert suchinformation to its original form, or to play back the storedinformation.

Such conversion of binary coded numbers to corresponding voltage signalsis achieved by the present invention in a very accurate, rapid andrelatively simple manner. Precision resistors are utilized as thestandard for reference. These precision resistors are used inconjunction with constant current devices, such as pentode vacuum tubes,whose high plate impedance insures constant current characteristics.

a present embodiment of the invention uses the above in a novelarrangement particularly adapted to the play back of stored informationof a seven digit code. In this embodiment the precision resistors areused to establish the voltage levels corresponding to each binary digit.The resistors are connected together to form a resistance string. Sevenconstant current input channels are used in conjunction with theresistance string. Each of the channels is connected to a point alongthe string to be hereinafter described. Each of the channels representsa digit in the code. An ammeter and variable resistance are provided ineach channel for accurately setting the current flow at the sainemagnitude in each channel when it is conducting. The varions channelsare controlled so as to make them conductive and non-conductivedepending upon the particular number to be converted to an amplitudevoltage signal. Thus channels which are conducting will produce avoltage drop across the resistance string determined by the magnitude ofthe various resistances, the current ow in each channel and the positionof the particular channel along the resistance string. By proportioningthe valves of the resistances in the string between the successivechannels so that the sum of the resistances, reading from one side ofthe string to the other, will vary between successive channels as ageometric progression with a ratio of two, voltage drops will occuracross the resistance string in equal increments for each succeedingnumber in the range of numbers covered by the code. For example, in thepresent instance of a seven digit code, the range of numbers is (ithrough 127. By proportioning resistance values as explained above, aparticular current value for the digit channels may be found whichprovides for a direct count of one volt per number; thus the number 12'?may be directly represented by 127 volts. While such a one volt pernumber scale is convenient for some applications, other proportions ofresistances and channel currents may be used to produce other desirableconversion scales.

In the present embodiment, vacuum tube pentodes maintain a constantcurrent in each of the seven current channels. A digital registeringcircuit, such as a bistable multivibrator, is connected to the controlgrid of each pentode in a manner to make the pentode either conductiveor completely nonconductive, depending on the code number beingrepresented. A clamping device, as a diode, is arranged between thecontrol grid and cathode of each pentode to insure a constant grid biaswhen the tube is conducting. The bistable multivibrators providing theregister circuits are triggered in accordance with the code number beingconverted. By their nature, they inherently maintain this code numberuntil cleared by a clearing circuit arangement for a new number to beregistered therein.

The foregoing and other advantages, objects and features of theinvention will be better understood from the following description takenin connection with the accompanying drawing, wherein:

Fig. 1 is a schematic view of a preferred embodiment of the inventionparticularly adapted automatically to convert stored binary code numbersto proportional voltage signals;

Fig. 2 is a graph illustrating the voltage output picture of theembodiment in Fig. l; and

Fig. 3 is a graph illustrating an alternate voltage output pictureobtainable from the embodiment in Fig. 1.

Referring to Fig. l in more detail, constant current devices, such asconstant current pentodes iii, l2, M, it, i8, and 22, each may bcconsidered as representing a digit in the binary code. For example, inthis instance, by representing a pentode by a 0 when it is conductingand a 1 when it is not conducting, the pentodes will represent numbersin binary code, some of which are as follows:

Pentodc Number Represented assures Thus the highest number which may berepresented in the present embodiment is 127, in which instance all ofthe pentodes are nonconductive. By adjusting variable resistances 24,26, 23, 32, 34 and 36 in the cathode circuits of pentodes l0, I2, I4,l5, I8, and 22, respectively, the current iiow in each pentode is set atthe same value. The adjustment and subsequent checking are facilitatedby providing an ammeter 38 in the plate circuit of each of the pentodes.Valuesof the resistances in the series resistance string are soproportioned that the sums of the individual resistances, reading frompoint 42 on one side of the string 4t to the point 44 on the other sideof the string 4t, follow a geometric progression having a ratio oi 2. Inthe present instance, a one-volt difference between points 42 and 44 ofthe resistance string 40 for each number in the code is obtained bymaking the value of resistances 45, 4t, Eil, 52, 54, 50 and 58 ofresistance string ait 1000 ohms, i000 ohms, 2000 ohms, 4000 ohms, 8000ohms, 16,000 ohms and 32,000 ohms, respectively, and the constantcurrent Value in each of pentodes I0, i2, I4, IE, i8, 20 and 22 onemilliampere. Thus 'the voltage drop between points 42 and itil, when allthe pentodes are con ducting, will be precisely i2? volts. By referringto the above table to determine those of the pentodes i0, i2, I4, IE5,I8, 20 and 22 which are con ducting for a given number, it will be seenthat those tubes conducting for the given number will. produce a voltagebetween points 42 and 44 equal to the complement of the number. Thus thenumber Bil represented in the pentodes will produce a one hundred andtwenty-seven minus B5 or a forty-two volt differential between points 42and 4d. By initially setting the voltage between points @il and b2, asby adjusting arm 5i on a variable voltage source as battery 63, atprecisely 12"! volts, the voltage between points 44 and 64 when all ofthe pentodes are conducting will be Zero. It will be noted from thetable above that when all oi the pentodes are conducting they representthe number zero. Further, the voltage between points 44 and t4 when allof the pentodes are nonconductive will be 127 volts which corresponds tothe number represented by all of the pentodes being nonconductive. Inlike manner, it seen 'from the table above that the voltage at point itwill vary between Zero and 127 with one-volt increments for succeedingnumbers represented by the pentodes. Intelligence voltage representingbinary numbers in the pentodes at may therefore be read directly orrecorded on a suitable indicator or recorder 63. The present embodimentpreferably incorporates a voltage regulator at the power source end ofthe voltage string i0 so as to insure the maintenance of a constantvoltage between points 42 and thereby prevent inaccuracies which mightbe due to long term power source fluctuations.

The pentodes i0, i2, i4, iii, ill, Eil and 22 are made conductive orcompletely ncnconductive by controlling the potential at control grids'50, l2, 14, lil, 30 and 82, respectively. This is done in the presentembodiment by providing register circuits, such as bistablemultivibrator circuits $4, 855, Si?, 90, 92, 94 and 95, respectively.Triggering pulses tt are used to trigger those bistable multivibrator-scorresponding to the coded number desired to be converted to amplitudevoltage intelligence. Those multivibrators triggered by a pulse 93 willcause a drop in potential in the corresponding control grid of thepentode sufficient to stop current flow in that pentode. Be-

d cause of the nature of the bistable multivibrator, this drop inpotential is maintained at the corresponding control grid until theparticular multi vibrator has been again triggered so as to return thepotential of the control grid to its conducting state. Triggering pulsesS3 in the present embodiment may be provided by any suitable means. Onesuch suitable means is a magnetic recording tape Iii upon which suitablecoded numbers have been recorded, as by magnetizing magnetic particleson the tape. These magnetized particles energize cored solenoids |02 asthe tape moves in the direction of the arrow. After ampliiication insuitable amplifiers [04 they appear as triggering pulses 98. It will benoted that, in addition to a solenoid 02 for each of the digits in thecode, an eighth cored solenoid leading to line it is used. The signal 98from this eighth solenoid is converted by a pulse forming circuit lillwhich may consist of a condenser tilt and resistance H0 into a clearingpulse H2 oi short duration which is led to each of the multivibrators84, 86, 88, 90, 92, 94 and Q5 which are thereby triggered so as toinsure the removal of any prior number before the registration of a newnumber from the recording tape iil. Thus, ior example, a pulse 93occurring at the bistable multivibrator 84 in response to a digit signalfrom the tape illil will cause a drop in potential in the control gridl0, as shown at H4. This reduced potential will be maintained at thecontrol grid lt, as shown at H6, until cleared by the pulse H2 so as tocause removal of the biasing potential as at HS. The pulse H2 may betimed from the recording strip itil so that it occurs simultaneouslywith the pulse 98 or so that it occurs before the pulses 98. If it ismade to occur simultaneously with the pulses e8, since it is of shorterduration than the pulses one of the pulses e8 will predominate and willdetermine the pulse position of the multivibrator., For example, if, fora particular number in one cycle, the pulse t8 occurred at the bistablemultivibrator 84 so as to cause a voltage drop i i4 at the control gridle, and for a succeeding number from the recording strip |00 it isnecessary that the control grid 'i0 be maintained at the negativepotential, then for the next number another pulse et will occursimultaneously with the clearing pulse H2. However, since the clearingpuise i i2 is of shorter duration than the pulse et, any triggeringcaused by pulse l i2 will be retriggered by the pulse S8 so that thecontrol grid 'it will continue to be maintained at the desired negativepotential. ln this simultaneous pulse system, successive numbers willappear in a continuous curve as in Fig. 2. If the clearing pulses H2 aremade to appear before a succeeding number, then the multivibrators willbe all triggered to a aero position before the new number arrives. Thus,in each instance, all of the pentodes will be conductive after eachnumber and will thereby cause a zero voltage at point 44 after eachnumber. This will produce a graphical amplitude picture on recorder 60,as shown in Fig. 3.

A clamping device H8, such as a diode, and a leakage resistance E20 areprovided between the control grid of each pentode and the negativepotential line 122, thereby insuring a constant biasing potential at thecontrol grids of the respective pentodes and minimizing variations incurrent intensity in the respective channels.

This invention is not limited to the particular details of constructionand processes described, as' many equivalents will suggest themselves tothose skilled in the art. It is accordingly desired that the appendedclaims be given a broad interpretation commensurate with the scope ofthe invention within the art.

What is claimed is:

1. A circuit for converting binary coded pulses to direct-currentvoltages comprising: a source of voltage; a plurality of resistors and avoltageindicating device connected in series across said source ofvoltage from the higher to the lower potential terminals thereof; saidresistors corresponding in number to the number of digits in the codeand having consecutive values following a predetermined geometricprogression; a plurality of constant current devices, likewisecorresponding in number to the number of digits in said code; one of theends of each of said constant current devices being connected to thelower potential terminal of said source of voltage; the other ends ofsaid constant current devices being successively connected,respectively, to the lower potential ends of said resistors; and meansfor controlling the conductivity of said constant current devices inaccordance with the patterns of said coded pulses.

2. A circuit for converting binary coded pulses to direct-currentvoltages comprising: a source of voltage; a plurality of resistors and avoltageindicating device connected in series across said source ofvoltage from the higher to the lower potential terminals thereof; saidresistors corresponding in number to the number of digits in the codeand having consecutive values following a geometric progression having aratio of 2; a plurality of constant current devices, likewisecorresponding in number to the number of digits in said code; one of theends of each of said constant current devices being connected to thelower potential terminal of said source of voltage; the other ends ofsaid constant current devices being successively connected,respectively, to the lower potential ends of said resistors; and meansfor controlling the conductivity of said constant current devices inaccordance with the patterns of said coded pulses.

3. A circuit for converting binary coded pulses to direct-currentvoltages comprising: a source of voltage; a plurality of resistors and avoltageindicating device connected in series across said source ofvoltage from the higher to the lower potential terminals thereof; saidresistors corresponding in number to the number of digits in the codeand having consecutive values following a predetermined geometricprogression; a plurality of electron discharge devices, likewisecorresponding in number to the number of digits in said code; thecathodes of said electron discharge devices being connected to the lowerpotential terminal of said source of voltage; the

anodes of said electron discharge devices being successively connected,respectively, to the lower potential ends of said resistors; and meansfor controlling the conductivity of said electron discharge devices inaccordance with the patterns of said coded pulses.

4. A circuit for converting binary coded pulses to direct-currentvoltages comprising; a source of voltage; a plurality of resistors and avoltageindicating device connected in series across said source ofvoltage from the higher to the lower potential terminals thereof; saidresistors corresponding in number to the number of digits in the codeand having consecutive values following the geometric progression1-1-2-4-8, etc.; a plurality of electron discharge devices, likewisecorresponding in number to the number of digits in said code; thecathodes of said electron discharge devices being connected to the lowerpotential terminal of said source of voltage; the anodes of saidelectron discharge devices being successively connected, respectively,to the lower potential ends of said resistors; and means for controllingthe conductivity of said electron discharge devices in accordance withthe patterns of said coded pulses,

5. A circuit for converting binary coded pulses to direct-currentvoltages comprising: a source of voltage; a plurality of resistors and avoltageindicating device connected in series across said source ofvoltage from the higher to the lower potential terminals thereof; saidresistors corresponding in number to the number of digits in the codeand having consecutive values following a predetermined geometricprogression; a plurality of constant current devices, likewisecorresponding in number to the number of digits in said code; one of theends of each of said constant current devices being connected to thelower potential terminal of said source of voltage; the other ends ofsaid constant current devices being successively connected,respectively, to the lower potential ends of said resistors; means forcontrolling the conductivity of said constant current devices inaccordance with the patterns of said coded pulses; and means forrestoring said constant current devices to their initial conditionsafter each action thereon by said coded pulses.

ANTHONY ABATE.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,608,527 Rainey Nov. 30, 1926 2,505,029 Carbrey Apr. 25, 19502,514,671 Rack July 11, 1950 2,581,426 Mason Jan. 8, 1952

